Increased demand for high-resolution projection displays makes the projector industry search for ways of enhancing the resolution above the native resolution of the projector's image panel. Resolution enhancement through superimposition is one method of enhancing the resolution that has gained popularity in the industry the last couple of years. This method consists of shifting every other projected frame spatially with sub-pixel precision, and by doing so creating a new pixel grid on the projected surface with smaller effective pixel pitch. There is still an open question of how well this technique performs in comparison to the native resolution, and how high the effective resolution gain really is. To determine which application the superimposition method is best suited for, it is also interesting to look at how this method performs over different kinds of image and video content. To help investigate these questions we have developed a simulator that simulates different superimposition methods over several classes of image content. The superimposed images are then evaluated by several image quality metrics with the goal of finding out which quality metrics are most applicable to the superimpositioning case. We found that the MSSSIM metric is the most suitable to evaluate superimposed images. VIF also performs quite well, but MSSSIM performs slightly better. However, none of these metrics identifies all the artefacts introduced by the superimpositioning. More research is needed to develop an ideal metric.